gistfile1.php

<?php

class OC_Hook extends ArrayObject {

	static protected $registered = array();
	protected $abort = false;
	protected $callbacks = array();
	protected $signal = '';

	public static function connect($classname, $signalname, $callback) {
		if(!isset(self::$registered[$signalname])) {
			self::$registered[$signalname] = array();
		}

		self::$registered[$signalname][$classname] = $callback;
	}

	public static function compact($parameters) {
		$c = __CLASS__;
		return new $c($parameters);
	}

	public static function emit($signalname, \OC_Hook $parameters = null) {
		if(empty($parameters)) {
			$parameters = \OC_Hook::compact(array());
		}
		if(isset(self::$registered[$signalname])) {
			$parameters->doEmit($signalname, self::$registered[$signalname]);
		}
	}

	public function doEmit($signalname, $callbacks) {
		$this->signal = $signalname;
		$this->callbacks = $callbacks;
		if(count($this->callbacks)) {
			$this->next();
		}
	}

	public function next() {
		$key = key($this->callbacks);
		$next = array_shift($this->callbacks);
		try {
			call_user_func($next, $this);
		}
		catch (\Exception $e) {
			// Log exception
			echo "Caught exception while running {$this->signal} for {$key}.\n";
		}
		if(!$this->abort && count($this->callbacks)) {
			$this->next();
		}
	}

	public function abort() {
		$this->abort = true;
	}

	public function has($key) {
		$key = is_array($key) ? $key : array($key);
		return count(array_intersect(array_keys($this->callbacks), $key)) > 0;
	}

	public function getSignal() {
		return $this->signal;
	}

	public function until($key, $callback) {
		while($this->has($key) && !$this->abort) {
			$this->next();
		}
		if(!$this->abort) {
			call_user_func($callback, $this);
		}
	}

}

OC_Hook::connect('foo', 'sig1', function(OC_Hook $params) {
	// wait until 'qux' fires, then abort
	$params->until('qux', function(OC_Hook $params){
		$params['new'] = 'This is newer.';
		$params->abort();
	});
});

OC_Hook::connect('bar', 'sig1', function(OC_Hook $params) {
	$params['new'] = 'This is new.';
	$params->next();
});

OC_Hook::connect('baz', 'sig1', function(OC_Hook $params) {
	$params['change'] = 'This is changed.';
});

OC_Hook::connect('qux', 'sig1', function(OC_Hook $params) {
	throw new \Exception('test hook exceptions');
});

OC_Hook::connect('quux', 'sig1', function(OC_Hook $params) {
	$params['new'] = 'This is too new.';
	// This one won't execute because abort() was called from foo
});


OC_Hook::emit('sig1', $result = OC_Hook::compact(array('change'=>'old value')));

extract($result->getArrayCopy());

var_dump($change, $new);